Mediterranean Sea Level Variability Changes and Mediterranean Sea Level Variability Changes and Projections at High Frequencies (1-100 Days)Projections at High Frequencies (1-100 Days)

Ivica VilibicIvica Vilibic, Jadranka Sepic, Jadranka SepicInstitut of Oceanography and Fisheries, Split, Institut of Oceanography and Fisheries, Split,

CroatiaCroatia

Gabriel Jordà, Marta MarcosGabriel Jordà, Marta MarcosIMEDEA (CSIC-UIB), Palma de Mallorca, SpainIMEDEA (CSIC-UIB), Palma de Mallorca, Spain

MotivationMotivation

1.1. More attention has been paid to the MSL projections More attention has been paid to the MSL projections than to sea level extremes.than to sea level extremes.

2.2. Regional sea level extreme climate projections are just Regional sea level extreme climate projections are just now ‘being born’ for the Mediterranean.now ‘being born’ for the Mediterranean.

3.3. What about short timescales (less than few months) What about short timescales (less than few months) contributors to the sea level variability (SLV) and contributors to the sea level variability (SLV) and extremes, about their present climate patterns and extremes, about their present climate patterns and future projections?future projections?

4.4. Does SLV climate projections differ over frequencies?Does SLV climate projections differ over frequencies?

To ‘slightly’ bridge that problem weTo ‘slightly’ bridge that problem we

1.1. Applied 2D ocean climate model to the Mediterranean, Applied 2D ocean climate model to the Mediterranean, forced by reanalysis atmospheric fields (hindcast run) forced by reanalysis atmospheric fields (hindcast run) and GHG+aerosol from RegCM (control run + B1, A1B, and GHG+aerosol from RegCM (control run + B1, A1B, A2 projections)A2 projections)

2.2. Extracted SLV patterns over different frequency bands Extracted SLV patterns over different frequency bands (1-3, 3-10, 10-100 days) by applying digital band-pass (1-3, 3-10, 10-100 days) by applying digital band-pass filtering to the sea level seriesfiltering to the sea level series

3.3. Estimated the importance (variance) of SLV over Estimated the importance (variance) of SLV over different frequency bands and associated atmospheric different frequency bands and associated atmospheric processesprocesses

4.4. Computed present and future SLV climatology and Computed present and future SLV climatology and linear trends.linear trends.

5.5. Assessed a difference between frequency bands, Assessed a difference between frequency bands, present climate and scenarios, and sub-basinspresent climate and scenarios, and sub-basins

The modelThe model

Type:Type: barotropic barotropicDomain:Domain: Mediterranean + a bite of Atlantic Mediterranean + a bite of AtlanticResolution:Resolution: 1/4 1/4oo x 1/61/6oo, 8660 grid nodes, 8660 grid nodesForcing:Forcing: wind and air pressure wind and air pressureHindcast run:Hindcast run: ARPEGE dynamical downscalling of ERA40, ARPEGE dynamical downscalling of ERA40,

1958-20011958-2001Climate runs:Climate runs: Control (1950-2000) + SRES B1, A1B, A2, Control (1950-2000) + SRES B1, A1B, A2,

ARPEGE-v3 RegCM (2000-2100)ARPEGE-v3 RegCM (2000-2100)

Hindcast model run has been validated over long-term Hindcast model run has been validated over long-term tide gauge records, separately for each frequency band.tide gauge records, separately for each frequency band.

Verification and reliability of the model resultsVerification and reliability of the model results

Good :)Good :)hm :(hm :(

Verification and reliability of the model resultsVerification and reliability of the model results

Control model run has been Control model run has been validated over hindcast validated over hindcast model run, separately for model run, separately for each frequency band.each frequency band.

Also done by Also done by Jorda et al. Jorda et al. (GPC, in press)(GPC, in press) on on reproduction of overall reproduction of overall seasonal cycle, intra- and seasonal cycle, intra- and inter-annual variability.inter-annual variability.

Relative difference in Relative difference in energy between control energy between control and hindcast model runs and hindcast model runs

Present climate SLV values (hindcast)Present climate SLV values (hindcast)

Present climate SLV trends (hindcast)Present climate SLV trends (hindcast)

Trends are mostly insignificant, Trends are mostly insignificant, although negative in average.although negative in average.

Present climate SLV trends (hindcast)Present climate SLV trends (hindcast)

Sporadically one Sporadically one may find significant may find significant negative trends negative trends over small areas over small areas within the domain.within the domain.

Future climate SLV trends (75p)Future climate SLV trends (75p)

1-3 d1-3 d

Trends are significantly negative!!!Trends are significantly negative!!!

Future climate SLV trends (99p)Future climate SLV trends (99p)

Less negative extreme SLV trends.Less negative extreme SLV trends.

Future climate SLV trends (spatial, seasonal)Future climate SLV trends (spatial, seasonal)

Conclusions and perspectivesConclusions and perspectives

Mediterranean ocean climate model Mediterranean ocean climate model reproduced wellreproduced well the 3- the 3-100-day SLV, and 100-day SLV, and not so goodnot so good the 1-3-day SLV – further the 1-3-day SLV – further downscalling of atmospheric CMdownscalling of atmospheric CM to capture properly local to capture properly local temporal and spatial changes in forcing should be carried out.temporal and spatial changes in forcing should be carried out.

The The largest SLV variancelargest SLV variance is occurring over is occurring over the planetary the planetary frequency bandfrequency band (10-100 days), from 60 to 85% over the (10-100 days), from 60 to 85% over the Mediterranean, emphasizing the importance of the associated Mediterranean, emphasizing the importance of the associated processes in overall sea level extremes.processes in overall sea level extremes.

Present Mediterranean SLVPresent Mediterranean SLV at periods between 1 and 100 days at periods between 1 and 100 days has mostly insignificant trendshas mostly insignificant trends..

Projected SLV trends are largely negativeProjected SLV trends are largely negative for A1B and A2 for A1B and A2 scenarios, and remained insignificant for B1 scenario.scenarios, and remained insignificant for B1 scenario.

Negative trends are larger for Negative trends are larger for the 1-3-day frequency bandthe 1-3-day frequency band and and during ONDduring OND – implication to overall sea level extremes. – implication to overall sea level extremes.

A broadening in A broadening in methodologymethodology (ensembles, fine analyses in (ensembles, fine analyses in frequency domain) is advised for future SLV studies.frequency domain) is advised for future SLV studies.